Begin by heating a large skillet to medium high heat. Coat with cooking oil.
Mix together the chicken breast chunks and cornstarch (or arrowroot) so the chicken pieces are completely coated. Toss in the skillet. Cook for about 5 minutes until chicken is browned, but not cooked through.
Make the sauce. In a small bowl, mix together soy sauce, hoisin, vinegar, sriracha, oil, chicken broth, sugar, and garlic cloves.
Place chicken in the slow cooker, top with sauce. Set your slow cooker to low and cook for 4 hours.
Top with crushed red pepper (if using) and serve over rice with green onion.